Nitrogen Enriched Air

Problem

Diesel engine exhausts are a major source of NOx, a regulated atmospheric pollutant.  EPA regulations are mandating substantial reductions in the NOx emissions from diesel engines.

Solution

NOx formation chemistry is extremely sensitive to the temperature reached in the diesel fuel combustion cycle.  Slight changes in the cylinder charge can dramatically alter the peak temperature and in turn the NOx generation. Compact Membrane Systems, Inc. supplies membranes that can alter the charge and substantially reduce the amount of NOx generated.  CMS’ process delivers nitrogen-enriched air (NEA) to the intake manifold by selectively permeating an oxygen-enriched stream (OEA) across the membrane.  

Results

Supplying NEA containing 82% nitrogen instead of air with 78% nitrogen has been shown to reduce the formation of NOx by 50%.

Benefits over alternative approaches

• Exhaust Gas Recycle also alters the cylinder charge, combustion temperature, and the NOx formation chemistry.  However EGR:
  • requires a high temperature exhaust cooler,
  • increases engine heat rejection load to cool exhaust prior to recycle,
  • recycles corrosive gases, soot, etc. into the engine intake,
  • reduces engine oil life, and
  • increases engine maintenance requirements.
    
• NOx Absorber Traps and Catalytic Aftertreatment Devices aim to reduce NOx emissions by treating the engine exhaust.  However they:
  • require careful temperature control on the exhaust stream,
  • are typically limited by to low sulfur fuels that are costly if available,
  • require supply of a reductant chemical such as ammonia or urea, or
  • require regeneration by periodically supplying a reducing gas by injecting diesel fuel into the exhaust

The simple NEA system described in the diagram above overcomes these limitations and restrictions.

Related Publications

S. Nemser, D. Stookey, J. Nelson, “Diesel Engine Nox Reduction Via Nitrogen-Enriched Air”, 2003 American Filtration & Separations Society Fall Topical Conference, Ann Arbor, MI, September 2003. (download .pdf)

Poola, R. B., D. E. Longman, J. L. Anderson, K. Stork, R. Sekar, K. Callaghan, S. Nemser, and R. Bell, “Membrane-Based Nitrogen-Enriched Air for NOx Reduction in Light-Duty Diesel Engines”, SAE Technical Paper Series, 2000-01-0228, presented at SAE 2000 World Congress, Detroit, Michigan, March 6-9, 2000.

Callaghan, Kevin. B, and Stuart M. Nemser, “Method of producing nitrogen enriched air”, US Patent 6,478,852, November 12, 2002.

Nemser, Stuart M., K. B. Callaghan, and T. Reppert, “Combustion engine air supply system”, US Patent 5,960,777, October 5, 1999.

Nemser, Stuart M., “Air-intake system for mobile engines”, US Patent 5,051,113, September 24, 1991.